Conventionally, there has been proposed an LED lighting device which converts an AC power into a DC power to dim up and down an LED according to a dimming signal supplied from the outside (see, e.g. Japanese Patent Publication No. 4,636,102). In this conventional example, it is controlled such that the LED is turned on or off at a predetermined dimming level during a predetermined time period immediately after the supply of the AC power. After the lapse of the predetermined time period, the LED is dimmed up or down according to the dimming signal supplied from the outside.
Meanwhile, a dimming signal generation device which continuously outputs a dimming signal for a while even after power is cut off has been disclosed as the prior art in FIG. 2 of Japanese Patent Application Publication No. H3-57196. In FIG. 1 of Japanese Patent Application Publication No. H3-57196, as its improved technology, there is disclosed an embodiment of the dimming signal generation device that has been modified such that the dimming signal is blocked before a source voltage of a discharge lamp lighting device is attenuated after the power is cut off.
In the technology disclosed in Japanese Patent Publication No. 4,636,102, the LED can be controlled to be turned on or off at the predetermined dimming level during the predetermined time period immediately after the supply of AC power. However, in a case where a plurality of lighting devices are controlled by one dimming signal generation device as shown in FIG. 4, it was necessary to provide a countermeasure circuit to each lighting device, resulting in an increase in the cost of the entire illumination control system.
Further, in order to solve such problem of the illumination control system, there has been proposed modifying the dimming signal generation device rather than the lighting device in Japanese Patent Application Publication No. H3-57196. However, since the dimming signal generation device is used in combination with the discharge lamp lighting device that requires a preheating operation when the power supply is turned on, it was not a configuration in which the dimming signal can be supplied immediately after the power supply is turned on.